The carmaker confirmed today that the most powerful version of the reborn soft-top roadster -- built on a platform that will be shared with the Toyota Supra -- will be a six-cylinder version wearing the M40i badge. That turbocharged engine has most recently been announced for the first M-badged version of the X3, in which it generates 265kW from 5500-6500rpm and 500Nm between 1520-4800rpm.
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BMW is believed to be just weeks away from launching the BMW X3 M40i in Australia.
The German luxury brand has teased the Z4 via a heavily disguised pre-production prototype during testing at the group’s test centre at Miramas in the south of France.
“Trials at the Autodrome de Miramas are focusing on fine-tuning of all drive and suspension systems – the basis for the sporty driving experience offered by the new BMW Z4,” BMW said. “The most intense form of new dynamic roadster performance is embodied by the BMW Z4 M40i.”
The most dynamically focused version of the Z4 will gain what BMW claims is an “extremely powerful in-line six-cylinder engine, a lowered sports suspension with electronically controlled dampers, a newly developed front axle, M light alloy wheels with mixed tyres, an M sports brake system and an electronically controlled lock in the rear axle differential”.
"The vehicle concept of the new BMW Z4 is geared consistently towards agility and driving dynamics," suspension engineering chief Jos van As said.
"The high level of body stiffness and the very rigid suspension attachment provide the perfect basis for a set-up that guarantees the performance qualities of a genuine sports car in terms of steering precision as well as longitudinal and transverse acceleration."
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According to BMW, the second-generation Z4 “will particularly introduce effective enhancements in terms of agile handling, spontaneity and precision when changing direction and accelerating in dynamic style out of bends – without losing out in the comfort disciplines”.
The M Performance-tuned B58 twin-scroll turbocharged in-line six that is expected to power the Z4 M40i has an extra 15kW over the previous version of the roadster to wear the badge, the Z4 M, powered by a normally aspirated S54 3.0-litre straight-six engine lifted from the E46 M3.
Whether the M40i will remain the performance flagship of the Z4 range or if it is due to be upstaged by an even more powerful pure M-variant remains to be confirmed by BMW.
The heavily disguised prototype also gives us clues that the 2019 version of the Z4 will tone down some of the wilder elements flagged in the 2017 Concept Z4 unveiled at Pebble Beach in the US last year.
The windscreen adopts a more conventional drop-top construction compared with the minimalist, frameless look of the Pebble Beach car, the slit-like bonnet vents are shelved, and the gaping maw of the air dams at either side of the wide, sharknose-styled grille are toned right down. The buttresses behind the seats are also replaced by conventional rollover hoops.
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However, some of the elements remain, such as the swept headlights and what appears to be a clamshell bonnet.
BMW appears to be preparing the Z4 for a full reveal later this year, either at the flagship Paris motor show in October, or at November’s Los Angeles motor show in recognition that the US is likely to be one of the roadster’s most popular markets outside of Europe.